Genius SP-HF1250X - 2.0 speakers

[bocca]

Hi all. First post in this section

My home speakers died recently.
First of all here are the specs from the official website



What's going on?
Well, one morning i turned on the speakers and there was a incredibly loud buzzing sound. Constant, deep and vibrating. Almost exactly the same as when you touch metal part of the computer case with the audio jack, but way louder.
I tried everything... Unplugging speakers from computer, changing cable, unplugging left speaker from the right (problem is in the right and main one), problem stays. As soon as it gets the power it starts with the noise and that's it.

So... I unscrewed it, and took some photos of the board for starters

[budm]

Re: Genius SP-HF1250X - 2.0 speakers

What are mounted on that heat sink? Transistors? need pictures of the whole board, top side.

[bocca]

Re: Genius SP-HF1250X - 2.0 speakers

I don't kknow what these are, but here's the pic attached

[bocca]

Re: Genius SP-HF1250X - 2.0 speakers

first two pictures are topside of the board. 1st is above the heatsink, and the second one is below.
But I'll make one whole, just to get my camera. Iphone camera will not do. Flash messes everything up

[budm]

Re: Genius SP-HF1250X - 2.0 speakers

That is the power amplifier IC TDA2030, there should be two of them for 2 channels.
The 8-pin IC is more likely to be dual-op amp (generic 4558 IC) for the preamplifiers to drive the power amps which drive the speakers.
The noise is from both speakers?

[bocca]

Re: Genius SP-HF1250X - 2.0 speakers

Yes, there is two of them, sharing the same heatsink. 8pin IC indeed is 4558.

I think the noise comes only from the main speaker but I have to check it out as soon as the afternoon nap passes Small apartment, can't wake everyone up

[budm]

Re: Genius SP-HF1250X - 2.0 speakers

If just one speaker is making noise, then the problem can be the power amp IC or the dual op-amp, but look real close at the solder joints first.

[bocca]

Re: Genius SP-HF1250X - 2.0 speakers

well it's generally sloppy soldering job... I'll do all the joints again and see if it helps

thanks

[bocca]

Re: Genius SP-HF1250X - 2.0 speakers

joints redone, checked, but to no avail...

Plugged in the speakers again and noise definitley comes from both

[ben7]

Re: Genius SP-HF1250X - 2.0 speakers

joints redone, checked, but to no avail...

Plugged in the speakers again and noise definitley comes from both

Try desoldering the OPAMP chip and see if there is no hum.

[budm]

Re: Genius SP-HF1250X - 2.0 speakers

Do you hear the noise with the Volume control is all the way down? You can also try heating or cooling the OP-Amp to see if it does have any affect on the noise.
One thing I do not see are the Cotrol panel board pictures, there should be some Op-amp for the Bass/Treble controls circuits.

[bocca]

Re: Genius SP-HF1250X - 2.0 speakers

I changed the op amp yesterday with brand new 4558. When i seitched everything back on noise was way quieter for about a second and then it was back on the loudest.

I guess it's not the op-amp

[ben7]

Re: Genius SP-HF1250X - 2.0 speakers

Perhaps a smaller filter cap is bad, causing the thing to self-oscillate.

[bocca]

Re: Genius SP-HF1250X - 2.0 speakers

well, i replaced both power amps, and all the smaller caps (9 of them, 2 types). Results - tonight

thanks!

[bocca]

Re: Genius SP-HF1250X - 2.0 speakers

no changes Only thing I didn;t replace are resistors and two big capacitors. I'm out of ideas

[budm]

Re: Genius SP-HF1250X - 2.0 speakers

I still do not get the response if the noise is there no matter what the Volume control or tone controls are set to. Are there more than one OP-AMP? Some thing bad that is common to both channels.

[ben7]

Re: Genius SP-HF1250X - 2.0 speakers

no changes Only thing I didn;t replace are resistors and two big capacitors. I'm out of ideas

Most likely the resistors will be fine.

I would be surprised if the rectifier bridge diodes are bad, although they might be cheapo-chinese rubber electrode ones.

Of course I'd replace the main filter caps also, if the rectifier is bad then the caps could be damaged also.

Can you take out the diodes and measure them with a diode-checker? (I'm referring to the big black ones)

[ben7]

Re: Genius SP-HF1250X - 2.0 speakers

On a side note, did you replace these caps did you?

They are used in the voltage regulator for the LM4558.

[bocca]

Re: Genius SP-HF1250X - 2.0 speakers

@budm:

I'm sorry. Somehow I completely skipped answering you. Yes, noise is there no matter what volume, bass or theble setting are.

@ben7:

I'll take them out today when I get to work and post the results.

As for the second post, yes, I replaced those 4 caps after I changed the LM4558.

[ben7]

Re: Genius SP-HF1250X - 2.0 speakers

@budm:

I'm sorry. Somehow I completely skipped answering you. Yes, noise is there no matter what volume, bass or theble setting are.

@ben7:

I'll take them out today when I get to work and post the results.

As for the second post, yes, I replaced those 4 caps after I changed the LM4558.

Do you have visual access to the speakers? If so, when you first plug them in, does the speaker cone suck in, and buzz? or does it push out? If they do one of those, unplug them immediately because there is DC voltage being fed to the speakers, and they wont do well with that!

Ok, do you have a multimeter?

If so, put your black probe where the black circle is, and measure each spot marked in red with the red probe. One should measure anywhere from 15v to 5v, and the other should measure anywhere from -15v to -5v. Please report back the readings.